An explosion in the Moscow subway today killed at least 39 people and injured more than 100 others. Russian officials say the blast was a terrorist attack, apparently caused by a bomb. But investigators say the explosion could also have been accidental. The blast is the latest in a series of attacks in the Russian capital that have been blamed on Chechen rebels and is raising anew the issue of safety on Moscow's public transportation system.

Prague, 6 February 2004 (RFE/RL) -- A blast in the Moscow subway during rush hour this morning killed at least 39 people and injured around 120, in what Russian officials suspect was a suicide-bomb attack.

The explosion took place at around 8:40 a.m. local time in a subway car between two stations on a busy line in southeast Moscow. It occurred in the second car of a subway train after it had pulled away from the Avtozavodskaya station and was heading north to Paveletskaya station, on the capital's circle line.

Moscow police spokesman Kirill Mazurin said the bombing is being investigated as an act of terrorism and that it may have been caused by a suicide bomber -- "a kamikaze terrorist," as he put it.

But the nature of the blast is not immediately clear.

"But the Russian security services and police are notoriously corrupt and ineffective and until now, [they are] not very effective in preventing terrorist attacks."

Deputy Moscow Mayor Valerii Shantsev says investigators have not found evidence of the shrapnel that would usually be part of such a bomb. "The explosion was caused by an explosive device which wasn't filled with any bullets or balls, so the metal structure of the wagon was damaged and the windows were blown out," he said. "The third wagon was damaged, too, and the people in the second and third wagons suffered from the blast."

He said the bomb was likely in a briefcase or a rucksack on the floor of the subway car.

A woman who was slightly injured in the blast described the incident to reporters after coming out of the subway. "There was an explosion in the second [subway] car," she said. "The driver told us there was a piece of flesh lying on the floor in the second car. For a long time, we couldn't open the doors. Then, finally, the driver opened them, and we started walking. We walked for about 2 kilometers. There was panic and a lot of screaming."

Deputy Interior Minister Aleksandr Chekalin, speaking to reporters, says at least 39 people were killed in the explosion and another 129 were injured.

But Emergency Situations Ministry officials told the Russian news agency ITAR-TASS that it was "next to impossible" to count exactly the number of dead.

Moscow Mayor Yurii Luzhkov announced he is cutting short a U.S. trip and returning to Moscow.

Meanwhile, Russian President Vladimir Putin, speaking during a meeting with visiting Azerbaijani President Ilham Aliyev, said that "terrorism is the plague of the 21st century" and appealed for international cooperation against it.

"I have no doubt that if we join our efforts -- bilaterally in the whole Caucasus region and internationally -- we will certainly be successful in this fight. And I have no doubt whatsoever that our law-enforcement agencies will be able to work effectively in this fight against terrorism," Putin said.

Putin indirectly linked the attack to Chechen guerrillas who may be trying to pressure him to negotiate with separatist leaders ahead of next month's (14 March) Russian presidential elections.

But Chechen separatist leader Aslan Maskhadov's envoy, Akhmed Zakaev, speaking with RFE/RL by telephone from London, denied any involvement: "The president [Maskhadov] and the government of the Chechen Republic officially declare that they have absolutely no connection with this provocation and condemn it unequivocally. Terrorism is not our method, and those who are trying to carry out their policies by intimidating society will suffer a fiasco in the end and will find themselves behind bars."

Deputy Interior Minister Chekalin said a joint investigation by Interior Ministry officials and agents of the Federal Security Service (FSB) is already under way. Chekalin also said security throughout the Moscow subway network has been stepped up.

Analysts say it is premature to blame the explosion on a certain terrorist group or even on Chechen rebels. Russian security expert Pavel Felgenhauer noted that both the nature and the circumstances of the blast remain obscured by confusion. "Even the Russian security services do not exclude that maybe this was an accident, [that] someone was carrying in the metro explosives or, maybe, inflammable [flammable] liquid that exploded," he said. "And if there was no shrapnel, maybe it was an accidental explosion. Maybe by terrorists, but maybe they were not intending to do that in the metro."

The explosion is the latest in a series of blasts that have rocked Moscow in recent years. In December, a female suicide bomber blew herself up outside the National Hotel across from Moscow's Red Square, killing at least five others. A double suicide bombing at a Moscow rock concert in July last year killed 16 people. Five days later, an aborted suicide-bomb attack at a central Moscow restaurant killed the sapper trying to defuse the bomb.

In October 2002, radical Chechen separatists took some 800 hostages in a Moscow theater, demanding that Russia withdraw from the breakaway republic. In the subsequent commando attack, all 41 separatists were killed. Some 129 hostages also died of gunshot wounds and the effects of the sleeping gas used to storm the theater.

In September 1999, bombs destroyed apartment blocks in Moscow and two other Russian cities, killing more than 200.

And in an attack closely resembling today's blast, four people were killed when a bomb exploded on 11 June 1996, in a subway train at the Tulskaya station in southern Moscow. That attack took place five days before a presidential election, which was subsequently won by then-incumbent Boris Yeltsin.

Russia's public transportation network has so far been rarely targeted by terrorists. But analyst Felgenhauer says it is virtually impossible to offer total protection against such attacks. Furthermore, he expressed concern about the poor record of Russia's security services in preventing terrorist attacks. "Security in Moscow actually is very lax and now apparently the authorities will do something to improve it," he said. "Although how effective that will be and how long the increased security measures will continue until something else happens, I don't know. But the Russian security services and police are notoriously corrupt and ineffective and until now, [they are] not very effective in preventing terrorist attacks."

But Felgenhauer says extra measures, such as those taken after the 1996 attack on the Moscow subway, when patrols checked subway trains at the end of the line, could help improve security.